Thermoelectric switch



Dec. 11, 1928. 1,695,103

A. U. HOOK THERMOELECTRIC SWITCH Filed May 16, 1927 /19 /za l 2 PE' 2530 I FIE 7 vi# 4.0 30 @num/Lto@ 33? ARLEY u- HaaK aftozum Patented Dec.1l, 1928.

vUNITED STATES ARLEY U. HOOK, OF NEW WASHINGTON, OHIO.

THEBMOELECTBIC SWITCH.

Application ,filed Hay 16,

This invention relates to improvements in thermo switches for electriccurrent and moreV particularly to devices for cutting oil' an felectriccurrent supply as soon as the desired 5,1 heat or objectionable heat iscreated.

An ob'ect of the invention is to form a simplifie device permittingadjustmentfor action at any desired degree of heat. An-

' other object of the inventlon is the construction of a simple devicefor making and breakin the circuit by a spring snap action. Other ojectsof the invention will be more' readily understood from the followingdescri t1on and the annexed drawings referred to t erein inlwhichz- Fig.1 shows the side view of the improved thermo-electric switch;

Fi 2, a lon itudinal section through they mid e of the evice;

Fig. 3, a top view of Fig. 2 showing the arrangement of the contactmembers and the shifting spring;

Fig. 4 is an end view of the device;

Fig. 5 is a section on line 5-5 of Fig. 3;

Fig. 6 is a plan view of the spring or shiftln member for the contactmembers; Fig, a side view of the spring shown in i 6.

shownz theswitch device comprises a hollow, boxlike frame member 2 openat the top and provided with upwardly extending end wal/ls 3 and 4. Thebottom or middle portion 5 connecting the end walls 3 and 4 is `slottedat 6, and a composite metal thermal bar 7 of U-form, connected by screws8 to the middle portion 5, extends through the slot to the inside offrame 2. The thermal bar is composed of two thin strips of differentmetals preferably cop er and zinc welded o together at both ends.k hefree end 9 of the thermal bar is upewardly bent to contact with a springmem r 10 of special shape which will later be particularly described. Asspecifically shown in Figls. 2 and 3, the spring member 10 is rigidlyeld at 11 in an adjustable supporting member or plate 12 connected toend wall 4 of body 2 by va screw -14 slidably confined in a slot 15 ofwall 4. The supporting member 12 may be vertically shifted to change theposition of the end support of spring 10, and in order to facilitatesuch shifting thev top portion of plate 12 is bent to form an abutmentfor an adjustingscrew 16 screwed into the bottom 5 of body 2 so thatslight loosening of screw saw cuts in the branches o 1927. Serial No.191,854.

14 will ermit a very accurate shifting of plate 12 y screw 16.

The end wall 3 of body 2 is bent rectangularly to form an offsetextension parallel to the bottom 5, and is divided into two partsy orprongs 18 and 19 by a slot 20 cut into this extension and extending intothe end wall'3. Slot 20 permits the spring 10 to extend outside of thebody 2 and said spring. 10 bears at its free end a contact plate 21adapted to engage contact plates 22 arranged on the prongs 18 and 19.

Spring member 10 is alsosupported by a second supporting member 23 ofyoke shape having grooves 24 for the edges of the sprin 10 engagedtherein. These rooves are smal the member 23 and are engaged byextensions 25 on the spring 10 and provide a rigid fulcrum supportpermitting slight pivotal movement of member 10 at the supporting oints.Supporting member 23 is also adjustable horizontally or lengthwise ofthe spring by an adjusting screw 26 screwed into end wall 3 andcooperating with screw 21 to support the member 23 on wall 3. Byadjustment of plate l2 and member 23 spring 10 may be put underpreliminary or normal tension so that contact plate 21 is closed withcontact plates 22', but under certain other circumstances a sudden shiftof member 10 mayoccur, causing .the end of spring member 10 bearingcontact plate 21 to travel sud- -denly a relatively large distance tobreak thecontact without great arcing, as mayy occur with direct currentby a relatively'- slow break.

The sha e of the sprin 10 is such, and the place o contact of the termal bar therewith is so chosen, that it will automatically spring backto its set position when the pressure of the thermal bar .is released.To achieve this purpose spring 10 is sharply bent close to its rigidsupport 12 at one end as at 40, and the bearing end of the thermal baron spring 10 is located quite close to said end of the spring. By thisarrangement a relatively small movement of the end of thermo band willelect a quick shift of member 10 and snap action of the switch. 105 Thefree or extended end of the spring 10 has a rib 3() pressed thereinwhich increases the stiffness or rigidity of the free end of the spring.

In operation, the pressure of the thermo un band under the inuence ofexcessive heat will bend the spring 10 until it passes center' and itwill then snap the contacts open. Vhen the pressure is released the kink40 in the spring will have the effect of restoring or snapping back thespring to original position thereby closing the contacts. If desired,the spring may be made without this kink, in which event the switch willremain open after actuation, if desired; but by pro- Vision of the kinkin the spring it will restore the circuit as before stated.

The adjustment of the plate l2 is important, as it permits a setting foroperation according to the desired temperature. That is, by adjustingthe plate one way or another by means of the screw 1G the position ofthe spring l0 relative to the expansion member 9 may be varied so muchthe temperature at which the spring will act to open the circuit. Thispermits the device to be used under various conditions or with differentappliances.

I claim:

1. A thermal switch having a spring fixed at one end and free at theother, the free end carrying a contact, and a support between the endsof the spring, the spring being bowed under tension between said supportand the xed end, and a thermal element bearing against the bowed part ofthe spring, the fixed end of the spring being adjustable crosswise ofthe spring Vto vary the pressure of the spring against the thermalelement.

2. A thermal switch as set forth in claim l, the free end of the springhaving a longitudinal rib to increase its stiffness.

3. A thermal switch comprising a frame having its endwall slotted androvided with two prongs extending outwar 1y from said wall7 a bowedspring in tension in the frame and projecting through the slot, and withits free end beside the prongs, contacts on the prongs and said end, anda. thermal element supported in the frame and bearing against thespring.

In testimony wlhereof, I do aix my signature.

ARLEY U. HOOK.

